Security forces have recovered evidence that suggests the blast in the Delhi-bound Shalimar Express was an act of sabotage. They also suspect not one but two blasts, including one over a railway bridge.

"The train had left Sambha Railway Station at 9:52 pm and was passing over a bridge when a blast occurred," a Northern Railway spokesman said in a statement in Delhi. Exhibiting presence of mind, the driver immediately applied emergency brakes to minimise the damage. However, the rear trolley of the engine and six coaches next to it derailed.

Another blast appeared to have occurred near the toilet area, which suffered damage along with some pellet marks in the S-6 coach.

Quoting state police sources, the spokerperson said the blast on the bridge was suspected to be an act of sabotage as "incriminating" evidence, including detonators, a grenade pin and empty AK-47 cartridges, were found nearby.

Intelligence officials said militants may have triggered the blast to divert the attention of the security forces and try to secure the release of one of their jailed associates.

This is not the first time that the Shalimar Express has come under attack.